The invention relates to a method for producing metals, in particular molten pig iron, steel pre-material or ferroalloys, from metal-oxide-containing raw material, the raw material being melted in a metallurgical vessel by means of at least one plasma burner directed from top to bottom, as well as to an arrangement for carrying out the method.
The processing of fine ores to liquid metal, with the reduction aggregates presently in use, requires pre-agglomeration. If, for instance, fine-grained iron ores are to be reduced and melted to liquid metal, which usually takes place in a blast furnace or in an electric reduction furnace, it is necessary, in order to achieve a yield as economical as possible and a good reduction performance with as low a fuel consumption as possible, to make the ore lumpy by sintering, pelletizing or briquetting.
This also holds for the production of ferroalloys (FeCr, FeMn, FeW, FeNi, FeSi, . . . ), which are melted primarily in electric reduction furnaces.
The disadvantages of these known methods are to be seen, among others, in the high technological and economic expenditures required for the treatment of the ores prior to the melting and reduction processes proper, and in the relatively long process time.
From Austrian patent No. 257,964, a method of the initially defined kind for the reduction of metallic oxides by means of an electric arc plasma is known. The plasma arc is struck between a plasma burner vertically arranged in the lid and a bottom electrode arranged in the bottom of a melting vessel.
The reduction of the metal oxides takes place in the slag layer by subjecting the molten oxide to the electric arc plasma jet containing a hydrocarbon gas, and by reducing this molten oxide by the decomposition products of the hydrocarbon gas.
This known method has the disadvantage that the thermal energy radiated off the plasma jet constitutes a great load on the furnace lining, since the strongest heat radiation occurs perpendicularly to the axis of the plasma jet. This involves a shorter furnace campaign, i.e., the operation time of the furnace from one bricking up to the next bricking up of the refractory lining, on the one hand, and a poor utilization of the energy supplied on the other hand, since a large part of the heat must be absorbed by the furnace brickwork without participating in the melting process.